First Lieutenant is one of three possible runners for Ireland, with the Dessie Hughes-trained Magnanimity and Irish National hero Lion Na Bearnai still in contention.

Hughes said: "Hopefully he'll run, unless the ground is too deep.

"I hear they are expecting a dry week after today, so by Saturday it might have dried out a bit."

Philip Hobbs has Planet Of Sound and Duke Of Lucca in the mix.

The weather will also dictate whether they, too, make the final field.

"Neither of them would want it too soft, so we'll have to make a decision later in the week. It's the same for everyone at the moment," said Hobbs.

As well as Tidal Bay, champion trainer Paul Nicholls has also confirmed Harry The Viking, but stable companion Michel Le Bon is a notable defection.

Other major players include The Package, Hold On Julio and Saint Are.

Last year's Hennessy hero Carruthers is also a possible runner - as is the 2010 winner Diamond Harry.

One horse for whom conditions should not pose too many problems is Friscot Depot, who was in the process of running a big race at Ascot on his debut for Charlie Longsdon when falling three fences from home.

Sam Waley-Cohen, son of part-owner Robert, will keep the ride this weekend.

Longsdon said: "It was the lightest Sam had ever ridden when he rode him last time.

"He will probably do 2lb over weight on the day and I think we will put a stronger bit in his mouth because he was a bit keen last time.

"I don't think the ground will be a problem as all his runs in Ireland were on heavy ground."

Although Tidal Bay has been given the go-ahead, Nicholls needs the rain to relent for Harry The Viking, who is partly owned by Sir Alex Ferguson.

He said: "Tidal Bay definitely runs and we'll be keeping an eye on the weather for Harry The Viking.

"The forecast is for it to dry up a bit so we could well be OK."

Newbury clerk of the course Richard Osgood told sportinglife.com: "We're currently Soft, Heavy in places and are due a little bit of light rain today. That should be the end of the rain for the week which is good, but it is getting slightly colder.

"There is the risk of a light frost and we'll cover the take-offs and landings as a precaution."